firmament

noun7

1. •
   (literary) The vault of the heavens, where the clouds, sun, moon, and stars can be seen; the heavens, the sky.

   • And thei that be wise, shal shine, as the brightnes of the firmament: & they that turne to righteousnes, shal shine as the starres, for euer and euer. — 1560
2. •
   (historical) In the geocentric Ptolemaic system, the eighth celestial sphere which carried the fixed stars; (countable, by extension) any celestial sphere.

   • [B]etweene the sphere of Saturne and the Firmament, there is such an incredible and vast space or distance (7000000. semidiameters of the earth, as Tycho [Brahe] calculates) void of starres: [...] — 1638
3. •
   The field or sphere of an activity or interest.
4. •
   The abode of God and the angels; heaven.

   • Praise ye the Lord. Praise God in his Sanctuarie: Praise him in the firmament of his power. — 1611
5. •
   A basis or foundation; a support.

   • Ten years ago, the Wall Street wirehouse brokerage firm seemed unassailable – part of the very firmament underpinning the entire investment industry from coast to coast. — 2012
6. •
   (no longer used) A piece of jewellery worn in a headdress with numerous gems resembling stars in the sky.

   • Pins tipt with Diamond Point, and head, / By which the Curls are fastened, / In radiant Firmament set out, / And all over the Hood sur-tout: [...] — 1690
7. •
   (no longer used) The act or process of making firm or strengthening.